Because of MPAA rules U.S. movie trailers cannot show blood, so blood is often colored black to gain approval. Trailers that do not obey this and other rules, such as; foul language and violent, sexual, or otherwise objectionable imagery may be issued a red band, which indicates approval for only “restricted” or “mature” audiences. These trailers may only be shown before R-rated, NC-17-rated, or unrated movies.